<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <title>03_流程控制</title>
</head>
<body>
<script>
    //1.顺序结构
    console.log('1');
    console.log('2');
    console.log('3');
    //2.分支结构
    let username = 'tom';
    //若用户名是空串''转为布尔是false,!false为true,会走分支1
    /*if (!username){
        alert('用户名不能为空!');
    }else {
        alert('用户名格式正确!');
    }*/
    //3.选择分支
    let gender = 0;
    switch (gender){
        case 1:
            console.log('男');
            break;
        case 0:
            console.log('女');
            break;
        default:
            console.log('未知');
    }
    //4.循环结构
    let names = ['张三','李四','王五','赵六','钱七'];
    for (var i = 0; i < names.length; i++) {
        console.log(names[i]);
    }
    //如果用var定义循环变量i,循环结束后在此处仍能打印出i的值
    //但如果用let定义,就会报错:变量i不存在
    console.log(i);

    //增强for循环
    for(let name of names){
        console.log(name)
    }
</script>
</body>
</html>